The present invention relates to an apparatus for controlling power distribution to devices, for example outlet strips, etc.
Outlet strips provide multiple outlets for one single outlet. Outlet strips are used in a variety of common places and businesses and households. Due to their wide use of applications, manufacturers are now producing specialized outlet strips. Some of these specialized outlet strips switch the power on and off to some of their outlets depending upon the current draw of one of the unswitched (control) outlets. When the current at the control outlet exceeds a preset threshold the switched outlets turn on. When the current draw falls below the same threshold, the switched outlets turn off. This can be accomplished by several different methods. If the device plugged into the control outlet draws more or less current than the threshold, this type of outlet strips works fine. However, when the device draws the same amount of current as the threshold, the outlet strip could oscillate the switched outlets. This would cause the device on the switched outlets to be turned on and off many times in a row and could cause damage to the devices. Some solutions related to the outlet strips are disclosed in U.S. patent application Ser. Nos. 09/521,029; 09/553,355; 09/953,743; U.S. Pat. No. 4,825,140.
Accordingly, it is an object of the present invention to provide an apparatus for controlling power distribution to the devices, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in an apparatus for controlling power distribution to the devices which has a power inlet to be connected to a power source; a primary power outlet to be connected to a primary device; at least one secondary power outlet to be connected to at least one secondary device; a primary power outlet to be connected to a primary device; at least one secondary power outlet to be connected to at least one secondary device; sensing means for sensing when a current level falls below a threshold in response to the primary device being turned off and when the current level raises above a threshold in response to the primary device being turned on; executing means operatively connected with said sensing means and operative for interrupting a power supply to said at least one secondary power outlet when said sensing means sends the currents level below the threshold and supplying power to said at least one secondary power outlet when said sensing means senses the current level above the threshold correspondingly; and means for setting the threshold for interrupting a power supply to said at least one secondary power outlet in response to the primary device being turned off lower than the threshold for supplying power to said at least one secondary outlet in response to the primary device being turned on.
When the apparatus is designed in accordance with the present invention, the on/off threshold would change into separate on threshold and off threshold. The switched outlets would turn on using a higher threshold than the turn off threshold. This type of arrangement which is based on hysteresis eliminates the possibility of relay chatter and/or oscillations due to current draw.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.